The present invention relates to a method of supervising an electrical line for short circuits and an arrangement of apparatus for performing such method. The preferred field of application of the invention is the supervision of high voltage lines in energy transmission networks.
Short circuits in electrical lines can be detected, for example, by supervising the input impedance of a section of the line, in particular the real component of such input impedance, i.e., the input resistance. It is possible, however, in extreme loading conditions, which in some circumstances are still acceptable but in any case would not be treated as a short circuit, that the input resistance can get into ranges of magnitude which overlap those of short circuiting conditions and which therefore, on the one hand, prevent a sufficiently reliable short circuit detection from being achieved but, on the other hand, do not prevent unnecessary circuit disconnections.
The object of the invention is therefore to provide a method of short circuit supervision, which, as compared with a mere supervision of the input resistance, is distinguished by a higher grade of discrimination between short circuit conditions and extreme loading conditions.
As will be more particularly described, it is possible that the amplitude relationships created in the proposed manner can be reproduced--as one of the possible types of quantities resulting from amplitude comparison--in the form of characteristics dependent upon the variable fault resistance or terminating resistance, thus making possible a clear distinction between the short circuit-region and the operating region.